JP2013014777A - Cyclic olefin compositions for temporary wafer bonding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new compositions and methods of using those compositions as bonding compositions.SOLUTION: The compositions comprise a cycloolefin copolymer dispersed or dissolved in a solvent system, and can be used to bond an active wafer to a carrier wafer or substrate to assist in protecting the active wafer and its active sites during subsequent processing and handling. The compositions form bonding layers that are chemically and thermally resistant, but that can also be softened or dissolved to allow the wafers to slide or be pulled apart at the appropriate stage in the fabrication process.

Description

  This invention was made with government support under contract number FA8650-05-D-5807 as determined by the Air Force Research Laboratory (AFRL). The United States government has certain rights to this invention.

  The present invention relates broadly to novel compositions and methods of using these compositions to form an adhesive composition that can support an active wafer on a carrier wafer or substrate during wafer thinning and other processing.

  Wafer thinning has been used to help electrical operation of integrated circuits (ICs) by dissipating heat. Thicker substrates cause increased capacitance, requiring thicker transmission lines and consequently a larger IC footprint. Substrate thinning increases impedance, while capacitance reduces impedance, reduces transmission line thickness, and consequently reduces IC dimensions. Thus, the thinning of the substrate facilitates the miniaturization of the IC.

  Geometric constraints are another motivation for substrate dilution. Via holes are carved on the back side of the substrate to facilitate contact on the front side. When making a via hole using a normal dry etching technique, geometrical constraints are applied. For substrates having a thickness of less than 100 μm, via holes with a diameter of 30-70 μm are made with minimal post-etch residue within the time allowed using dry etching techniques. For thick substrates, larger diameter via holes are required. This requires a longer dry etching time and creates a greater amount of post-etch residue, thus significantly reducing throughput. Larger via holes require a greater amount of metal spraying at the same time, which is more expensive. Therefore, with respect to the back surface processing, the thin substrate can be processed faster and cheaper.

  Thin substrates can be cut and scored more easily to make an IC. A thin substrate requires less labor because the amount of material to penetrate and cut is smaller. Whatever method (saw cutting, scribing and breaking, or laser cutting) is used, the IC is easier to cut from a thin substrate. Most semiconductor wafers are thinned after front side processing. For ease of handling, the wafer is processed (ie, the front side device) at its normal full thickness, eg 600-700 μm. When completed, they are thinned to 100-150 μm. In some cases (eg, when a gallium arsenide (GaAs) substrate is used for high power devices), the thickness may be reduced to 25 μm.

  Mechanical thinning of the substrate is performed by contacting the wafer surface with a hard, flat rotating horizontal disk containing a liquid slurry. The slurry may include a polishing medium with a chemical etchant such as ammonia, fluoride, or combinations thereof. The abrasive provides "rough" substrate removal, i.e. thinning, while the etchant chemistry promotes "polishing" at the submicron level. The wafer is maintained in contact with the medium until a predetermined amount of substrate is removed and the target thickness is reached.

  For wafers with a thickness of 300 μm or more, the wafer is held in place by a machine tool using a vacuum chuck or some form of mechanical attachment. If the wafer thickness is reduced to less than 300 μm, it will be difficult or impossible to maintain control over attachment and wafer handling if further thinning and processing is attempted. In some cases, mechanical devices can be made that attach and hold to thinned wafers, but these are subject to many problems, especially when the process varies. For this purpose, the wafer (“active” wafer) is mounted on another rigid (carrier) substrate or wafer. This substrate becomes a holding platform for further thinning and processing after thinning. The carrier substrate is composed of materials such as sapphire, quartz, certain glasses, and silicon, and typically exhibits a thickness of 1000 μm. The selection of the substrate depends on how close the coefficient of thermal expansion (CTE) between the materials is. However, currently available bonding methods do not have sufficient thermal or mechanical stability to withstand the high temperatures encountered in backside processing processes such as thermal spraying or dielectric welding and annealing. Furthermore, many current methods have poor flatness (which causes excessive variation in the total thickness across the wafer diameter) and poor chemical resistance.

  One method used to secure the active wafer to the carrier substrate is through a heat dissipating adhesive tape. This processing method has two major drawbacks. First, the tape thickness uniformity across the active wafer / substrate interface is limited, and this uniformity limit is often insufficient for handling very thin wafers. Second, heat dissipating adhesives will soften at low temperatures such that the wafer / carrier substrate stack bonded to many typical wafer processing steps performed at higher temperatures cannot be tolerated.

  On the other hand, thermally stable adhesives often require excessively high adhesion pressures or temperatures in order to obtain a sufficient melt flow to produce good adhesion morphology. Similarly, excessive mechanical force may be required to separate the active and carrier wafers because the viscosity of the adhesive is still too high at realistic peel temperatures. Furthermore, thermally stable adhesives may be difficult to remove without leaving a residue.

US Patent No. 6008298 US Pat. No. 5,191,026

  There is a need for new compositions and methods for adhering active wafers to carrier substrates, which can withstand high processing temperatures and allow immediate separation of the wafer and substrate at the appropriate stage of the processing process.

  The present invention broadly provides a wafer bonding method that overcomes the problems of the prior art, including providing a stack composed of first and second substrates adhesively bonded via an adhesive layer, and first And separating the second substrate. The adhesive layer is formed from a composition containing a cycloolefin copolymer (COC) dissolved or dispersed in a solvent system.

  The present invention further provides an article comprising first and second substrates and an adhesive layer. The first substrate is comprised of a back surface and an active surface comprised of at least one active site and a plurality of topographical features. The second substrate has an adhesive surface. The adhesive layer is adhered to the active surface of the first substrate and the adhesive surface of the second substrate. The adhesive layer is formed from a composition comprising a cycloolefin copolymer dissolved or dispersed in a solvent system.

  In an additional embodiment, the present invention relates to a composition useful for bonding and bonding two substrates. The original composition is composed of a cycloolefin copolymer dissolved or dispersed in a solvent system and an additive component. The additive component is selected from the group consisting of tackifying resins, low molecular weight cycloolefin copolymers, and mixtures thereof.

Fig. 3 illustrates the inventive method of thinning and peeling two wafers according to the present invention. FIG. 5 is a flow diagram illustrating representative processing steps followed by an example. 2 is a graph depicting the results of rheological analysis of an adhesive composition according to the present invention peeled at 150 ° C. FIG. 2 is a graph depicting the results of rheological analysis of an adhesive composition according to the present invention peeled at 200 ° C. FIG. 3 is a graph depicting the results of rheological analysis of an adhesive composition according to the present invention peeled at 250 ° C.

  More specifically, this inventive composition comprises a cycloolefin copolymer (COC) dissolved or dispersed in a solvent system. The copolymer is preferably present in the composition at a level of from about 5% to about 85% by weight, based on the total weight of the composition as 100% by weight, and from about 5% to about 85% by weight. 60% is more preferred, with about 10% to about 40% by weight being most preferred.

Suitable copolymers are preferably thermoplastic and have a weight average molecular weight (M _w ) of from about 2000 Daltons to about 200,000 Daltons, more preferably from about 5000 Daltons to about 100,000 Daltons. Suitable copolymers preferably have a softening temperature (melt viscosity at 3000 Pa · S) of at least about 100 ° C, more preferably at least about 140 ° C, and even more preferably at least about 160 ° C to about 220 ° C. . Suitable copolymers further preferably have a glass transition temperature (T _g ) of at least about 60 ° C, more preferably from about 60 ° C to about 200 ° C, and from about 75 ° C to about 160 ° C. Most preferred.

Suitable cycloolefin copolymers are composed of cyclic and acyclic olefin repeating monomers, or ring-opening polymers based on cyclic olefins. Preferred cyclic olefins for use in the present invention are selected from the group consisting of olefins based on norbornene, olefins based on tetracyclododecene, olefins based on dicyclopentadiene, and derivatives thereof. Is done. Derivatives are alkyl (C ₁ -C ₂₀ alkyls are preferred, C ₁ -C ₁₀ alkyls are more preferred), alkylidenes (C ₁ -C ₂₀ alkylidenes are preferred, C ₁ -C ₁₀ alkylidenes are more preferred) Aralkyl (C ₆ -C ₃₀ aralkyl is preferred, C ₆ -C ₁₈ aralkyl is more preferred), cycloalkyl (C ₃ -C ₃₀ cycloalkyl is preferred, C ₃ -C ₁₈ cycloalkyl is more preferred. ), Ether, acetyl, aromatic, ester, hydroxy, alkoxy, cyano, amide, imide, and silyl-substituted derivatives. Particularly suitable cyclic olefins used in the present invention include
And those selected from the group consisting of the foregoing combinations, wherein each R ₁ and R ₂ is independently —H, and alkyl groups (C ₁ -C ₂₀ alkyls are preferred, C ₁ -C ₁₀ Each R ₃ is individually —H, substituted or unsubstituted aryl groups (preferably C ₆ -C ₁₈ aryls), alkyl groups (C ₁ -C ₂₀ alkyls are preferred, C ₁ -C ₁₀ alkyls are more preferred), cycloalkyl groups (C ₃ -C ₃₀ cycloalkyls are preferred, C ₃ -C ₁₈ cycloalkyls are more preferred), aralkyl groups _(C 6 _{-C 30} aralkyl are preferable, more benzyl, phenethyl, and phenylpropyl, and C ₆ -C ₁₈ aralkyl groups, such as equal Masui), esters Motorui, ethers Motorui, acetyl groups, alcohols (C ₁ -C ₁₀ alcohols are preferred), an aldehyde group, ketones, nitriles, and is selected from the group consisting of combinations The

Suitable acyclic olefins are selected from the group consisting of branched and unbranched C ₂ -C ₂₀ alkenes (preferably C ₂ -C ₁₀ alkenes). More preferably, suitable acyclic olefins for use in the present invention are
Having the following structure, wherein each R ₄ is individually selected from the group consisting of —H and alkyl groups (preferably C ₁ -C ₂₀ alkyls, more preferably C ₁ -C ₁₀ alkyls): . Particularly preferred acyclic olefins for use in the present invention include those selected from the group consisting of ethene, propene, and butene, with ethene being most preferred.

Methods for producing cycloolefin copolymers are known in the art. For example, cycloolefin copolymers can be produced by chain polymerization of repeating and non-repeating monomers (such as norbornene and ethene shown below).
The reaction shown above results in an ethene-norbornene copolymer containing alternating norbornanediyl and ethylene units. Examples of copolymers produced by this method include TOPAS ^™ manufactured by Goodfellow Corporation and TOPAS Advanced Polymers, and APEL ^™ manufactured by Mitsui Chemicals. A suitable method for producing these copolymers is disclosed in US Pat. No. 6,0082,988, incorporated herein by reference.

Cycloolefin copolymers can be produced by further ring-opening metathesis polymerization of various cyclic monomers as illustrated below followed by hydrogenation.
Polymers of this type of polymerization can conceptually be considered as copolymers of ethene and cyclic olefin monomers (such as alternating units of ethylene and cyclopentane-1,3-diyl as shown below).
Examples of copolymers produced by this method include ZEUMOR ^{™ from} Zeon Chemicals and ARTON ^{™ from} JSR. Suitable methods for making these copolymers are disclosed in US Pat. No. 5,191,026, herein incorporated by reference.

Thus, the copolymer according to the invention is:
(I)
And preferably contains repeating monomers of the aforementioned combination, where:
Each R ₁ and R ₂ is independently selected from the group consisting of —H, and alkyl groups (preferably C ₁ -C ₂₀ alkyls, more preferably C ₁ -C ₁₀ alkyls); ₃ is individually -H, substituted or unsubstituted aryl groups (C ₆ -C ₁₈ aryls are preferred), alkyl groups (C ₁ -C ₂₀ alkyls are preferred, and C ₁ -C ₁₀ alkyls are more preferred. ), a cycloalkyl group such _(C 3 _{-C 30} cycloalkyl are _preferable, C 3 _{-C 18} cycloalkyls are more preferred), an aralkyl group such _(C 6 _{-C 30} aralkyl are preferable, benzyl, phenethyl, and phenylpropyl, more preferably C ₆ -C ₁₈ aralkyl group such that like the like), esters Motorui, ethers Motorui, acetyl groups, _(Preferably C 1 _{-C 10} alcohols) alcohols, aldehyde groups, ketones, nitriles, and combinations thereof,
And (II)
here:
----- is a single or double bond; and each R ₄ is individually -H and an alkyl group (preferably C ₁ -C ₂₀ alkyl, more preferably C ₁ -C ₁₀ alkyl); Selected from the group consisting of

The ratio of monomer (I) to monomer (II) in the polymer is preferably from about 5:95 to about 95: 5, more preferably from about 30:70 to about 70:30.
This ingenious composition is formed by simply mixing the cycloolefin copolymer and all other additive components with a solvent system, preferably from room temperature to about 150 ° C. for about 1 to 72 hours.

  The composition should contain at least about 15% by weight solvent system, preferably from about 30% to about 95% by weight, based on the total weight of the composition being 100% by weight, A solvent system of about 40% to about 90% is more preferred, and a solvent system of about 60% to about 90% by weight is even more preferred. The boiling point of the solvent system should be about 50-280 ° C, preferably about 120-250 ° C. Suitable solvents include methyl ethyl ketone (MEK) and cyclopentanone, as well as limonene, mesitylene, dipentene, pinene, bicyclohexyl, cyclododecene, 1-tert-butyl-3,5-dimethylbenzene, butylcyclohexane, cyclooctane, cyclo Hydrocarbon solvents selected from the group consisting of heptane, cyclohexane, methylcyclohexane, and mixtures thereof include, but are not limited to.

  The total solids level in the composition should be at least about 5% by weight, preferably about 5% to about 85% by weight, based on the total weight of the composition as 100% by weight, More preferably from about 5% to about 60% by weight, and even more preferably from about 10% to about 40% by weight.

  According to the present invention, the composition can include additional additive components, including low molecular weight cycloolefin copolymer (COC) resins and / or tackifying resins or rosins. The composition may further comprise several optional additive components selected from the group consisting of plasticizers, antioxidants, and mixtures thereof.

When low molecular weight COC is used in the composition, it is preferably present in the composition at a level of about 2% to about 80% by weight, based on the total weight of the composition being 100% by weight, More preferably from about 5% to about 50% by weight, and even more preferably from about 15% to about 35% by weight. The term “low molecular weight cycloolefin copolymer” refers to COCs having a weight average molecular weight (M _w ) of less than about 50,000 daltons, preferably less than about 20,000 daltons, and more preferably from about 500 to about 10,000 daltons. It is intended. Such copolymer preferably further has a T _g from about 50 ° C. to about 120 ° C., more preferably from about 60 ° C. to about 90 ° C., about 60 ° C. to about 70 ° C. being most preferred. A typical low molecular weight COC resin used in the present invention is commercially available from Topas Advanced Polymers under the name TOPAS ^™ Toner ™ (M _w 8000).

When a tackifier or rosin is utilized, it is preferably present at a level of about 2% to about 80% by weight, based on the total weight of the composition being 100% by weight, and about 5% by weight. % To about 50% is more preferred, and about 15% to about 35% by weight is even more preferred. The tackifier is selected from those having chemical properties compatible with the cycloolefin copolymer so that phase separation does not occur in the composition. Examples of suitable tackifiers include polyterpene resins (sold by Arizona Chemical under the name SYLVARES ^™ TR resin), β-polyterpene resins (sold by Arizona Chemical under the name SYLVARES ^™ TR-B resin), styrenated terpene resins (sold by Arizona Chemical under the name Zonatac NG resin), polymerized rosin resins (sold by Arizona Chemical under the name SYLVAROS ^TM PR resin), Eastotac ^TM rosin ester resins (Eastman Chemical Co. Sold under the name of the resin), alicyclic hydrocarbon resins (from Eastman Chemical under the name of PLASTOLYN ^TM resin, or Arakawa) a Commercially available under the name ARKON ^™ resin from Chemical, C5 aliphatic hydrocarbon resins (sold under the name PICCOTAC ^™ resin from Eastman Chemical), Hydrogenated hydrocarbons (named REGALITE ^™ resin from Eastman Chemical) ), And mixtures thereof, but are not limited to these.

When antioxidants are utilized, they are preferably present in the composition at a level of about 0.1% to about 2% by weight, based on the total weight of the composition being 100% by weight. More preferably, from about 0.5% to about 1.5% by weight. Examples of suitable antioxidants include phenolic antioxidants (pentaerythritol tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl sold under the name IRGANOX ^™ 1010 by the company Ciba). ) Propionate, etc.), phosphite antioxidant (such as tris (2,4-ditert-butylphenyl) phosphite sold under the name IRGAFOS ^™ 168 from Ciba), phosphonite antioxidant ( Tetrakis (2,4-di-tert-butylphenyl) [l, l-biphenyl] -4,4′-diylbisphosphonite, etc.) sold under the name IRGAFOX ^™ P-EPQ by Ciba, and these Including those selected from the group consisting of:

In another embodiment, the composition comprises bis (trimethoxysilylethyl) benzene, aminopropyltri (alkoxysilanes) (eg, aminopropyltri (methoxysilane), aminopropyltri (ethoxysilanes), --phenylamino Propyltri (ethoxysilane)), and other silane coupling agents, or mixtures thereof are essentially free of adhesion promoters (less than about 0.1% and preferably about 0% by weight). It is. In some embodiments, the final composition is also a thermoplastic (ie, not crosslinkable). Thus, in these alternative embodiments, the composition is essentially free of cross-linking agents such as Cytec's POWDERLINK ^™ and Hexion Specialty Chemicals' EPI-CURE ^™ 3200 (about by weight). Less than 0.1% and preferably about 0%).

  According to one embodiment, the melt viscosity (complex viscosity coefficient) of the final composition is preferably less than about 100 Pa · S, more preferably less than about 50 Pa · S, and from about 1 Pa · S to about 35 Pa · S. Even more preferably. For these measurements, the melt viscosity is determined via rheological kinetic analysis (TA Instruments AR-2000, two parallel plate configurations with a plate diameter of 25 mm). Furthermore, the melt viscosity is preferably determined at a suitable stripping temperature for the composition in question. The term “preferred stripping temperature” for the composition used here is determined by dynamic measurements at an oscillation frequency of the composition having a melt viscosity of less than 100 Pa · S and a temperature gradient of 1 Hertz. When the composition is measured at a suitable release temperature, the storage modulus (G ') of the composition is also preferably less than about 100 Pa, preferably less than about 50 Pa, and more preferably from about 1 Pa to about 26 Pa. The storage modulus is determined by dynamic measurements at a vibration frequency with a temperature gradient of 1 Hertz.

  The composition is thermally stable up to about 350 ° C. Further, the weight loss of the composition after 1 hour at a suitable stripping temperature plus 50 ° C. (preferably a temperature of about 200 ° C. to about 300 ° C.) depends on the composition, but is preferably less than about 5% by weight, More preferably, it is less than about 1.5%. In other words, at this temperature, there is little or no thermal decomposition of the composition as determined by the thermogravimetric analysis (TGA) described herein.

  The composition can be applied first to either the carrier substrate or the active wafer, but is preferably applied first to the active wafer. These compositions can be applied to achieve thick films without voids required for coating on stepped wafers and to achieve the required uniformity across the wafer. A suitable coating method involves spin coating of the composition with a spin speed of about 500-5000 rpm (more preferably about 1000-3500 rpm), an acceleration of about 3000-10000 rpm / second, and a spin time of about 30-180 seconds. Of course, the coating stage can be varied to achieve a specific thickness.

  After coating, the solvent can be evaporated by firing the substrate (eg on a hot plate). A typical calcination is at a temperature of about 70-250 ° C., preferably about 80-240 ° C. for a time of about 1-60 minutes, more preferably about 2-10 minutes. The film thickness after firing is generally at least about 1 μm (at the top of the microstructure), more preferably about 10-200 μm.

  After firing, the desired carrier substrate is brought into contact with and pressed against this inventive composition layer. The carrier substrate is heated to a temperature of about 100-300 ° C., preferably about 120-180 ° C., to adhere to the inventive composition. This heating is preferably carried out under vacuum for a time of about 1 to 10 minutes with a binding force of about 0.1 to about 25 kilonewtons. The bonded wafer can be exposed to processing steps related to back grinding, metal spraying, patterning, passivation, via hole formation, and / or wafer thinning, as described in more detail below.

  Illustrated in FIG. 1 (a) is a representative stack 10 that includes an active wafer 12 and a carrier wafer or substrate 14. Of course, the stack 10 is not drawn to scale and is exaggerated for purposes of this illustration. The active wafer 12 has an active surface 18. As shown in FIG. 1 (a), the active surface 18 can include various microstructured features 20a-20d. A typical active wafer 12 can include any microelectronic substrate. Some possible active wafer 12 examples include micromachined technology (MEMS) devices, display devices, flexible substrates (eg, vulcanized epoxy substrates, winding substrates that can be used to form maps), composite semiconductors, low k dielectric layers, dielectric layers (eg, silicon oxide, silicon nitride), ion implant layers, and silicon, aluminum, tungsten, tungsten silicide, gallium arsenide, germanium, tantalum, tantalum nitrite, SiGe, and mixtures thereof Including those selected from the group consisting of:

The carrier substrate 14 has an adhesive surface 22. A typical carrier substrate 14 is sapphire, ceramics, glass, quartz, aluminum, silver, silicon, glass-ceramic composites (such as products sold under the name Zerodure ^™ available from Schott AG), And a material selected from the group consisting of these combinations.

  Wafer 12 and carrier substrate 14 are adhesively bonded via an adhesive composition layer 24. Adhesive layer 24 is formed of the cycloolefin copolymer composition described above and is also applied and dried as described above. As shown in FIG. 1A, the adhesive layer 24 is adhered to the active surface 18 of the wafer 12 as well as the adhesive surface 22 of the substrate 14. Unlike prior art tapes, the adhesive layer 24 is a uniform (chemically the same) material throughout its thickness. In other words, the entire adhesive layer 24 is formed of the same composition.

  It is clear that the adhesive composition 24 can be applied to the active surface 18 by spin coating or spray coating so that the adhesive composition flows in and on various microstructured features. Furthermore, the adhesive layer 24 forms a uniform layer on the microstructure of the active surface 18. In order to explain this point, FIG. 1 shows a plane designated by a broken line 26 substantially parallel to the end portion 21 and the back surface 16. The distance from this plane to the bonding surface 22 is represented by the thickness “T”. The length across the flat surface 26 and substrate 14 of thickness “T” varies by less than about 20%, but is preferably less than about 10%, more preferably less than about 5%, and even more preferably less than about 2%. Most preferred is less than about 1%.

  The wafer package can now be subjected to subsequent thinning (or other processing) as shown in FIG. 1 (b), where 12 'represents the wafer 12 after thinning. Obviously, the substrate can be thinned to a thickness of less than about 100 μm, preferably to less than about 50 μm, more preferably to less than about 25 μm. After thinning, specific backside processing can be performed, including backside grinding, patterning (eg, photolithography, via hole etching), passivation, and metal spraying, and combinations thereof.

  Conveniently, the dried layer of this inventive composition has several highly desirable properties. For example, the gas releasing property is low with respect to the vacuum etching process. That is, if a 15-μm thick film of this composition is baked at 80-250 ° C. for 2-60 minutes (more preferably 2-4 minutes), the solvent is expelled from the composition and the subsequent 140-300 ° C. The change in film thickness upon firing for 2-4 minutes will be less than about 5%, preferably less than about 2%, and even more preferably less than about 1% or even 0% (referred to as “film shrinkage test”). ) Thus, the dried layer can be heated to a temperature of about 350 ° C., preferably up to about 320 ° C., and more preferably up to about 300 ° C. without causing a chemical reaction in the layer. In some embodiments, the layer can be further exposed to a polar solvent (eg, N-methyl-2-pyrrolidone) at a temperature of 80 ° C. for 15 minutes without reaction.

  The integrity of the dry layer adhesion is maintained by exposure to acids and bases. That is, even if a dry layer having a thickness of about 15 μm is immersed in an acidic medium (for example, concentrated sulfuric acid) or a base (for example, 30 wt% KOH) at 85 ° C. for about 45 minutes, the integrity of adhesion is maintained. be able to. Adhesion integrity can be assessed by using a glass carrier substrate and visually checking the adhesive composition layer over the glass carrier substrate to check for bubbles, voids, and the like. Furthermore, the integrity of the bond is maintained if the active wafer and carrier substrate cannot be separated by hand.

  After the desired processing is performed, the active wafer or substrate can be separated from the carrier substrate. In one embodiment, the active wafer and substrate are separated by heating to a temperature sufficient to soften the adhesive layer. More specifically, the stack is heated to a temperature of at least about 100 ° C, preferably to at least about 120 ° C, more preferably from about 150 ° C to about 300 ° C. These temperature ranges represent suitable stripping temperatures for the adhesive composition. This heating causes the adhesive composition layer to soften as shown in FIG. 1 (c) to form a softened adhesive composition layer 24 ′, at which point the two substrates are separated by, for example, sliding to the side. it can. FIG. 1 (c) shows an axis 28 that penetrates both the wafer 12 and the substrate 14, and a sliding force is usually applied in a direction transverse to the axis 28. Instead of sliding, the wafer 12 can be separated from the substrate 14 by lifting upwards (ie, the wafer 12 or substrate 14 generally away from each other).

  Alternatively, instead of heating and softening the layer, the adhesive composition can be dissolved using a solvent. As soon as the layer is dissolved, the active wafer and substrate can be separated. Suitable solvents used to dissolve the adhesive layer are all solvents that were part of the composition prior to drying as selected from the group consisting of MEK and cyclopentanone, as well as limonene, mesitylene, A hydrocarbon solvent selected from the group consisting of dipentene, pinene, bicyclohexyl, cyclododecene, 1-tert-butyl-3,5-dimethylbenzene, butylcyclohexane, cyclooctane, cycloheptane, cyclohexane, methylcyclohexane, and mixtures thereof But you can.

  Whether the adhesive composition is softened or dissolved, the separation simply applies a force that slides and / or lifts one of the wafers 12 or the substrate 14 and at the same time resists the slipping or lifting forces on the other. Obviously, this can be accomplished by maintaining the stop position (eg, applying opposite sliding or lifting forces to the wafer 12 and the substrate 14 simultaneously). This can be achieved with conventional tools.

  Any adhesive composition remaining in the device area can be removed by rinsing with a suitable solvent followed by spin drying. Suitable solvents include those listed above as suitable solvents for stripping as well as all original solvents that were part of the composition prior to drying. Any remaining composition is completely dissolved by exposure to the solvent for 5-15 minutes (at least about 98%, preferably at least about 99%, and more preferably about 100%). It is also acceptable to remove all residual adhesive composition using either plasma etching alone or in combination with a solvent removal process. After this stage, a clean, adhesive-free wafer 12 'and carrier substrate 14 remain (not shown in these clean states).

  The examples that follow illustrate preferred methods according to the present invention. However, it should be understood that these examples are provided for illustrative purposes and that none of them limits the overall scope of the present invention.

Example 1 Cycloolefin Copolymer Resin and Low Molecular Weight COC Resin Blend In this example, a formulation comprising a cycloolefin copolymer and a low molecular weight COC resin was made. In some formulations, an antioxidant was added.

<1. Sample 1.1>
In this procedure, 1.2 grams of ethene-norbornene copolymer (TOPAS ^™ 5010, T _g 110 ° C .; obtained from TOPAS Advanced Polymers, Florence, KY) in 6 grams of D-limonene (Florida Chemical). Dissolved with 2.8 grams of low molecular weight cycloolefin copolymer (TOPAS ^™ Toner ™, M _w 8000, M _w / M _n 2.0). The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

<2. Sample 1.2>
In this procedure, 0.75 grams of ethene-norbornene copolymer (TOPAS ^™ 8007, T _g 78 ° C) and 3.25 grams of low molecular weight COC (TOPAS ^™ Toner ™) are dissolved in 6 grams of D-limonene. did. The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

<3. Sample 1.3>
For this procedure, 1.519 grams of ethene-norbornene copolymer (TOPAS ^™ 5013, T _g 134 ° C.) was placed in 5.92 grams of D-limonene, 2.48 grams of low molecular weight cycloolefin copolymer ( TOPAS ^™ Toner ™), 0.04 grams of phenolic antioxidant (IRGANOX ^™ 1010), and 0.04 grams of phosphonite antioxidant (IRGAFOX ^™ P-EPQ). The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

<4. Sample 1.4>
In this procedure, 1.2 grams of ethene-norbornene copolymer (TOPAS ^™ 8007) was mixed with 5.81 grams of low molecular weight cycloolefin copolymer (TOPAS ^™ Toner ™) in 5.92 grams of D-limonene, Dissolved with 0.04 grams of phenolic antioxidant (IRGANOX ^™ 1010), and 0.04 grams of phosphonite antioxidant (IRGAFOX ^™ P-EPQ). The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

<5. Sample 1.5>
In this procedure, 2.365 grams of ethene-norbornene copolymer (TOPAS ^™ 5013) was transferred to 1.635 grams of low molecular weight cycloolefin copolymer (TOPAS ^™ Toner ™) in 5.92 grams of D-limonene. , 0.04 grams of phenolic antioxidant (IRGANOX ^™ 1010), and 0.04 grams of phosphonite antioxidant (IRGAFOX ^™ P-EPQ). The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

<6. Sample 1.6>
In this procedure, 2.2 grams of a hydrogenated norbornene based copolymer (ZEONOR ^™ 1060, T _g 100 ° C .; obtained from Zeon Chemicals, Louisville, KY) prepared by ring opening polymerization and 1.8 grams Of low molecular weight cycloolefin copolymer (TOPAS ^™ Toner ™) was dissolved in 5.92 grams of cyclooctane (Aldrich, Milwaukee, WI). The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

Example 2 Blend of Cycloolefin Copolymer Resin and Tackifier In this example, a formulation comprising a cycloolefin copolymer blended with various tackifiers was made. As in Example 1, antioxidants were added to some formulations.

<1. Sample 2.1>
In this procedure, 0.83 grams of ethene-norbornene copolymer (TOPAS ^™ 8007) was placed in 5.92 grams of D-limonene, 3.17 grams of a hydrogenated hydrocarbon resin (REGALITE ^™ R1125; Eastman Chemical Company, Obtained from Kingsport, Tennessee), 0.04 grams of phenolic antioxidant (IRGANOX ^™ 1010), and 0.04 grams of phosphonite antioxidant (IRGAFOX ^™ P-EPQ). The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

<2. Sample 2.2>
For this procedure, 0.7 grams of ethene-norbornene copolymer (TOPAS ^™ 8007) and 3.3 grams of styrenated terpene resin (ZONATA ^™ NG98; obtained from Arizona Chemical, Jacksonville, FL). Dissolved in 92 grams of D-limonene with 0.04 grams of phenolic antioxidant (IRGANOX ^™ 1010) and 0.04 grams of phosphonite antioxidant (IRGAFOX ^™ P-EPQ). The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

<3. Sample 2.3>
In this procedure, 1.9 grams of ethene-norbornene copolymer (TOPAS ^™ 5013) was placed in 5.92 grams of D-limonene and 2.1 grams of alicyclic hydrocarbon resin (ARKON ^™ P-140; Arakawa). Dissolved with Chemical USA, Chicago, Illinois), 0.04 grams of phenolic antioxidant (IRGANOX ^™ 1010), and 0.04 grams of phosphonite antioxidant (IRGAFOX ^™ P-EPQ) . The solution was stirred at room temperature until the added ingredients were in solution.

<4. Sample 2.4>
In this procedure, 2.42 grams of ethene-norbornene copolymer (TOPAS ^™ 5013) was placed in 5.92 grams of D-limonene, 1.58 grams of alicyclic hydrocarbon resin (PLASTOLYN ^™ R-1140; Arakawa Chemical USA, obtained from Chicago, Illinois), dissolved with 0.04 grams of phenolic antioxidant (IRGANOX ^™ 1010), and 0.04 grams of phosphonite ester antioxidant (IRGAFOX ^™ P-EPQ) did. The solution was stirred at room temperature until the added ingredients were in solution. The solid content of the solution was about 40%.

Example 3 Coating, Adhesion and Peeling and Analysis The formulations prepared in Examples 1 and 2 above were spin coated onto various substrate wafers. After baking to evaporate the solvent and reflow the adhesive composition, the second wafer was bonded to each coated wafer by applying pressure. A representative procedure for temporary wafer bonding using an adhesive composition is illustrated in FIG. The bonded wafers were tested for mechanical strength, thermal stability, and chemical resistance. Wafers were tested for delamination by manually sliding them aside at an acceptable temperature. After stripping, the adhesive composition residue was cleaned using a solvent rinse and spin.

The rheological properties of each formulation according to Examples 1 and 2 were tested. All these materials were successfully tested for delamination. The preferred stripping temperature for samples 1.1, 1.2, 2.1, and 2.2 was determined to be 150 ° C. The preferred stripping temperature for samples 1.3, 1.4, and 2.3 was 200 ° C. and the preferred stripping temperature for samples 1.5, 1.6, and 2.4 was 250 ° C. The storage modulus (G ′) and melt viscosity (η ^* , complex coefficient of viscosity) of each sample at its preferred release temperature are recorded below. Furthermore, the rheological data at each stripping temperature is illustrated in FIGS.

  In addition, further studies on thermal stability and chemical resistance were also conducted on these compositions. Thermogravimetric analysis (TGA) was performed with a TA Instruments thermogravimetric analyzer. TGA samples were obtained by scraping from the spin coat and fired adhesive compositions of Examples 1 and 2. For isothermal TGA measurements, the thermal stability of a particular adhesive composition was determined by heating the sample in nitrogen at a rate of 10 ° C./min to its preferred release temperature plus 50 ° C. and holding at that temperature for 1 hour. . The isothermal measurements for each sample formulation are recorded in Table 2 below. For scanning TGA measurements, the samples were heated from room temperature to 650 ° C. at a rate of 10 ° C./min in nitrogen.

Table 2 Isothermal thermogravimetric analysis results-thermal stability (within N ₂ )

  As can be seen from the table above, all COC-low molecular weight COC resin blends (Example 1) have the required thermal stability to at least 300 ° C., with minimal weight loss (<1.5 wt%). ). The average weight loss of the COC-tackifier blend (Example 2) was about 5 wt% when kept at the test temperature. However, as shown in Table 3 below, the 1 wt% weight loss temperature is higher than their respective adhesion / peeling temperatures, suggesting sufficient heat resistance for wafer bonding applications.

Table 3 Scanning thermogravimetric analysis results

  In order to determine chemical resistance, two silicon wafers were bonded using the specific bonding composition being tested. The bonded wafers were placed in a chemical bath of N-methyl-2-pyrrolidone (NMP) or 30% by weight KOH at 85 ° C. and concentrated sulfuric acid at room temperature to determine chemical resistance. Adhesion integrity was visually observed after 45 minutes to determine the stability of the adhesive composition for each chemical. All adhesive compositions maintained adhesion integrity.

Claims (6)

Applying the adhesive composition to either the first substrate or the second substrate by spin coating, wherein the layer is a uniform material across the thickness formed from the composition; and Bonding the wafer through the first and second substrates together.   The method of claim 1, wherein the first substrate is an active wafer having an active surface including microstructure features on a surface to which a layer is applied.   The method of claim 2, wherein the adhesive composition flows in and on microstructured features.   The method of claim 2, wherein the adhesive layer forms a uniform layer over the microstructure of the active surface.   The adhesive layer has a length across the second substrate of adhesive layer thickness “T” of less than about 20%, preferably less than about 10%, more preferably less than about 5%, even more preferably less than about 2%, most The method of claim 1, wherein the method is applied to vary preferably less than about 1%.   The method of claim 1, wherein the adhesive layer is applied by spray coating.